Can’t you just right click?
Can you distribute Mac software over the internet without signing it, thereby avoiding Developer ID and notarization entirely? Technically, currently, yes, although Apple has indicated that a future version of macOS may not allow unsigned code to run at all. Some people claim that Mac users can just right click" to run unsigned software. But what does that mean exactly? Let's look at the user experience, in a series of screenshots. For illustration, I created an unsigned application, MyGreatApp", uploaded it to my server, and then downloaded the app with Safari on macOS 10.15.6, the latest public version of the Mac operating system. (The experience is essentially the same on the beta version of macOS Big Sur, except the new iOS style alerts look even worse.) Here's what you see when you try to open the app normally (double click) in Finder.
[...]As a Mac developer, it's nearly impossible to run a viable software business when this is the first-run experience of new customers. You'll never get any new customers! This is why every Mac developer I know signs up for Developer ID and ships only signed, notarized apps. It would be financial suicide to do otherwise. Technically, the option is there to just right click", but practically it's not a viable distribution option for Mac developers. From a business perspective, there's no avoiding the Gatekeeper.
For all intents and purposes, Macs and macOS are already entirely locked down and can only run software approved by Apple. macOS Big Sur on ARM Macs will make the rules even stricter - while ARM Macs can still run unsigned Intel code in the way described above, you can't run unsigned code compiled for Apple Silicon.
The screws are being tightened little by little, and just as I predicted and warned way back in 2010 with the introduction of the Mac App Store (and then again in 2011 with the introduction of sandboxing, and then again in 2012 with the introduction of Gatekeeper), we're very close to a total lockdown of macOS, thereby completing turning the Mac into iOS - appliances you do not control and do not own. You pay a hefty sum for the mere privilege of borrowing your iOS or Mac appliance, but you don't actually buy them.